Imported Upstream version 5.18.0.246

Former-commit-id: 0c7ce5b1a7851e13f22acfd379b7f9fb304e4833

external/llvm/lib/IR/Dominators.cpp

@@ -0,0 +1,391 @@
+//===- Dominators.cpp - Dominator Calculation -----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements simple dominator construction algorithms for finding
+// forward dominators.  Postdominators are available in libanalysis, but are not
+// included in libvmcore, because it's not needed.  Forward dominators are
+// needed to support the Verifier pass.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/IR/Dominators.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/GenericDomTreeConstruction.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+using namespace llvm;
+
+// Always verify dominfo if expensive checking is enabled.
+#ifdef EXPENSIVE_CHECKS
+bool llvm::VerifyDomInfo = true;
+#else
+bool llvm::VerifyDomInfo = false;
+#endif
+static cl::opt<bool, true>
+    VerifyDomInfoX("verify-dom-info", cl::location(VerifyDomInfo), cl::Hidden,
+                   cl::desc("Verify dominator info (time consuming)"));
+
+bool BasicBlockEdge::isSingleEdge() const {
+  const TerminatorInst *TI = Start->getTerminator();
+  unsigned NumEdgesToEnd = 0;
+  for (unsigned int i = 0, n = TI->getNumSuccessors(); i < n; ++i) {
+    if (TI->getSuccessor(i) == End)
+      ++NumEdgesToEnd;
+    if (NumEdgesToEnd >= 2)
+      return false;
+  }
+  assert(NumEdgesToEnd == 1);
+  return true;
+}
+
+//===----------------------------------------------------------------------===//
+//  DominatorTree Implementation
+//===----------------------------------------------------------------------===//
+//
+// Provide public access to DominatorTree information.  Implementation details
+// can be found in Dominators.h, GenericDomTree.h, and
+// GenericDomTreeConstruction.h.
+//
+//===----------------------------------------------------------------------===//
+
+template class llvm::DomTreeNodeBase<BasicBlock>;
+template class llvm::DominatorTreeBase<BasicBlock, false>; // DomTreeBase
+template class llvm::DominatorTreeBase<BasicBlock, true>; // PostDomTreeBase
+
+template struct llvm::DomTreeBuilder::Update<BasicBlock *>;
+
+template void llvm::DomTreeBuilder::Calculate<DomTreeBuilder::BBDomTree>(
+    DomTreeBuilder::BBDomTree &DT);
+template void llvm::DomTreeBuilder::Calculate<DomTreeBuilder::BBPostDomTree>(
+    DomTreeBuilder::BBPostDomTree &DT);
+
+template void llvm::DomTreeBuilder::InsertEdge<DomTreeBuilder::BBDomTree>(
+    DomTreeBuilder::BBDomTree &DT, BasicBlock *From, BasicBlock *To);
+template void llvm::DomTreeBuilder::InsertEdge<DomTreeBuilder::BBPostDomTree>(
+    DomTreeBuilder::BBPostDomTree &DT, BasicBlock *From, BasicBlock *To);
+
+template void llvm::DomTreeBuilder::DeleteEdge<DomTreeBuilder::BBDomTree>(
+    DomTreeBuilder::BBDomTree &DT, BasicBlock *From, BasicBlock *To);
+template void llvm::DomTreeBuilder::DeleteEdge<DomTreeBuilder::BBPostDomTree>(
+    DomTreeBuilder::BBPostDomTree &DT, BasicBlock *From, BasicBlock *To);
+
+template void llvm::DomTreeBuilder::ApplyUpdates<DomTreeBuilder::BBDomTree>(
+    DomTreeBuilder::BBDomTree &DT, DomTreeBuilder::BBUpdates);
+template void llvm::DomTreeBuilder::ApplyUpdates<DomTreeBuilder::BBPostDomTree>(
+    DomTreeBuilder::BBPostDomTree &DT, DomTreeBuilder::BBUpdates);
+
+template bool llvm::DomTreeBuilder::Verify<DomTreeBuilder::BBDomTree>(
+    const DomTreeBuilder::BBDomTree &DT);
+template bool llvm::DomTreeBuilder::Verify<DomTreeBuilder::BBPostDomTree>(
+    const DomTreeBuilder::BBPostDomTree &DT);
+
+bool DominatorTree::invalidate(Function &F, const PreservedAnalyses &PA,
+                               FunctionAnalysisManager::Invalidator &) {
+  // Check whether the analysis, all analyses on functions, or the function's
+  // CFG have been preserved.
+  auto PAC = PA.getChecker<DominatorTreeAnalysis>();
+  return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>() ||
+           PAC.preservedSet<CFGAnalyses>());
+}
+
+// dominates - Return true if Def dominates a use in User. This performs
+// the special checks necessary if Def and User are in the same basic block.
+// Note that Def doesn't dominate a use in Def itself!
+bool DominatorTree::dominates(const Instruction *Def,
+                              const Instruction *User) const {
+  const BasicBlock *UseBB = User->getParent();
+  const BasicBlock *DefBB = Def->getParent();
+
+  // Any unreachable use is dominated, even if Def == User.
+  if (!isReachableFromEntry(UseBB))
+    return true;
+
+  // Unreachable definitions don't dominate anything.
+  if (!isReachableFromEntry(DefBB))
+    return false;
+
+  // An instruction doesn't dominate a use in itself.
+  if (Def == User)
+    return false;
+
+  // The value defined by an invoke dominates an instruction only if it
+  // dominates every instruction in UseBB.
+  // A PHI is dominated only if the instruction dominates every possible use in
+  // the UseBB.
+  if (isa<InvokeInst>(Def) || isa<PHINode>(User))
+    return dominates(Def, UseBB);
+
+  if (DefBB != UseBB)
+    return dominates(DefBB, UseBB);
+
+  // Loop through the basic block until we find Def or User.
+  BasicBlock::const_iterator I = DefBB->begin();
+  for (; &*I != Def && &*I != User; ++I)
+    /*empty*/;
+
+  return &*I == Def;
+}
+
+// true if Def would dominate a use in any instruction in UseBB.
+// note that dominates(Def, Def->getParent()) is false.
+bool DominatorTree::dominates(const Instruction *Def,
+                              const BasicBlock *UseBB) const {
+  const BasicBlock *DefBB = Def->getParent();
+
+  // Any unreachable use is dominated, even if DefBB == UseBB.
+  if (!isReachableFromEntry(UseBB))
+    return true;
+
+  // Unreachable definitions don't dominate anything.
+  if (!isReachableFromEntry(DefBB))
+    return false;
+
+  if (DefBB == UseBB)
+    return false;
+
+  // Invoke results are only usable in the normal destination, not in the
+  // exceptional destination.
+  if (const auto *II = dyn_cast<InvokeInst>(Def)) {
+    BasicBlock *NormalDest = II->getNormalDest();
+    BasicBlockEdge E(DefBB, NormalDest);
+    return dominates(E, UseBB);
+  }
+
+  return dominates(DefBB, UseBB);
+}
+
+bool DominatorTree::dominates(const BasicBlockEdge &BBE,
+                              const BasicBlock *UseBB) const {
+  // If the BB the edge ends in doesn't dominate the use BB, then the
+  // edge also doesn't.
+  const BasicBlock *Start = BBE.getStart();
+  const BasicBlock *End = BBE.getEnd();
+  if (!dominates(End, UseBB))
+    return false;
+
+  // Simple case: if the end BB has a single predecessor, the fact that it
+  // dominates the use block implies that the edge also does.
+  if (End->getSinglePredecessor())
+    return true;
+
+  // The normal edge from the invoke is critical. Conceptually, what we would
+  // like to do is split it and check if the new block dominates the use.
+  // With X being the new block, the graph would look like:
+  //
+  //        DefBB
+  //          /\      .  .
+  //         /  \     .  .
+  //        /    \    .  .
+  //       /      \   |  |
+  //      A        X  B  C
+  //      |         \ | /
+  //      .          \|/
+  //      .      NormalDest
+  //      .
+  //
+  // Given the definition of dominance, NormalDest is dominated by X iff X
+  // dominates all of NormalDest's predecessors (X, B, C in the example). X
+  // trivially dominates itself, so we only have to find if it dominates the
+  // other predecessors. Since the only way out of X is via NormalDest, X can
+  // only properly dominate a node if NormalDest dominates that node too.
+  int IsDuplicateEdge = 0;
+  for (const_pred_iterator PI = pred_begin(End), E = pred_end(End);
+       PI != E; ++PI) {
+    const BasicBlock *BB = *PI;
+    if (BB == Start) {
+      // If there are multiple edges between Start and End, by definition they
+      // can't dominate anything.
+      if (IsDuplicateEdge++)
+        return false;
+      continue;
+    }
+
+    if (!dominates(End, BB))
+      return false;
+  }
+  return true;
+}
+
+bool DominatorTree::dominates(const BasicBlockEdge &BBE, const Use &U) const {
+  Instruction *UserInst = cast<Instruction>(U.getUser());
+  // A PHI in the end of the edge is dominated by it.
+  PHINode *PN = dyn_cast<PHINode>(UserInst);
+  if (PN && PN->getParent() == BBE.getEnd() &&
+      PN->getIncomingBlock(U) == BBE.getStart())
+    return true;
+
+  // Otherwise use the edge-dominates-block query, which
+  // handles the crazy critical edge cases properly.
+  const BasicBlock *UseBB;
+  if (PN)
+    UseBB = PN->getIncomingBlock(U);
+  else
+    UseBB = UserInst->getParent();
+  return dominates(BBE, UseBB);
+}
+
+bool DominatorTree::dominates(const Instruction *Def, const Use &U) const {
+  Instruction *UserInst = cast<Instruction>(U.getUser());
+  const BasicBlock *DefBB = Def->getParent();
+
+  // Determine the block in which the use happens. PHI nodes use
+  // their operands on edges; simulate this by thinking of the use
+  // happening at the end of the predecessor block.
+  const BasicBlock *UseBB;
+  if (PHINode *PN = dyn_cast<PHINode>(UserInst))
+    UseBB = PN->getIncomingBlock(U);
+  else
+    UseBB = UserInst->getParent();
+
+  // Any unreachable use is dominated, even if Def == User.
+  if (!isReachableFromEntry(UseBB))
+    return true;
+
+  // Unreachable definitions don't dominate anything.
+  if (!isReachableFromEntry(DefBB))
+    return false;
+
+  // Invoke instructions define their return values on the edges to their normal
+  // successors, so we have to handle them specially.
+  // Among other things, this means they don't dominate anything in
+  // their own block, except possibly a phi, so we don't need to
+  // walk the block in any case.
+  if (const InvokeInst *II = dyn_cast<InvokeInst>(Def)) {
+    BasicBlock *NormalDest = II->getNormalDest();
+    BasicBlockEdge E(DefBB, NormalDest);
+    return dominates(E, U);
+  }
+
+  // If the def and use are in different blocks, do a simple CFG dominator
+  // tree query.
+  if (DefBB != UseBB)
+    return dominates(DefBB, UseBB);
+
+  // Ok, def and use are in the same block. If the def is an invoke, it
+  // doesn't dominate anything in the block. If it's a PHI, it dominates
+  // everything in the block.
+  if (isa<PHINode>(UserInst))
+    return true;
+
+  // Otherwise, just loop through the basic block until we find Def or User.
+  BasicBlock::const_iterator I = DefBB->begin();
+  for (; &*I != Def && &*I != UserInst; ++I)
+    /*empty*/;
+
+  return &*I != UserInst;
+}
+
+bool DominatorTree::isReachableFromEntry(const Use &U) const {
+  Instruction *I = dyn_cast<Instruction>(U.getUser());
+
+  // ConstantExprs aren't really reachable from the entry block, but they
+  // don't need to be treated like unreachable code either.
+  if (!I) return true;
+
+  // PHI nodes use their operands on their incoming edges.
+  if (PHINode *PN = dyn_cast<PHINode>(I))
+    return isReachableFromEntry(PN->getIncomingBlock(U));
+
+  // Everything else uses their operands in their own block.
+  return isReachableFromEntry(I->getParent());
+}
+
+void DominatorTree::verifyDomTree() const {
+  // Perform the expensive checks only when VerifyDomInfo is set.
+  if (VerifyDomInfo && !verify()) {
+    errs() << "\n~~~~~~~~~~~\n\t\tDomTree verification failed!\n~~~~~~~~~~~\n";
+    print(errs());
+    abort();
+  }
+
+  Function &F = *getRoot()->getParent();
+
+  DominatorTree OtherDT;
+  OtherDT.recalculate(F);
+  if (compare(OtherDT)) {
+    errs() << "DominatorTree for function " << F.getName()
+           << " is not up to date!\nComputed:\n";
+    print(errs());
+    errs() << "\nActual:\n";
+    OtherDT.print(errs());
+    errs() << "\nCFG:\n";
+    F.print(errs());
+    errs().flush();
+    abort();
+  }
+}
+
+//===----------------------------------------------------------------------===//
+//  DominatorTreeAnalysis and related pass implementations
+//===----------------------------------------------------------------------===//
+//
+// This implements the DominatorTreeAnalysis which is used with the new pass
+// manager. It also implements some methods from utility passes.
+//
+//===----------------------------------------------------------------------===//
+
+DominatorTree DominatorTreeAnalysis::run(Function &F,
+                                         FunctionAnalysisManager &) {
+  DominatorTree DT;
+  DT.recalculate(F);
+  return DT;
+}
+
+AnalysisKey DominatorTreeAnalysis::Key;
+
+DominatorTreePrinterPass::DominatorTreePrinterPass(raw_ostream &OS) : OS(OS) {}
+
+PreservedAnalyses DominatorTreePrinterPass::run(Function &F,
+                                                FunctionAnalysisManager &AM) {
+  OS << "DominatorTree for function: " << F.getName() << "\n";
+  AM.getResult<DominatorTreeAnalysis>(F).print(OS);
+
+  return PreservedAnalyses::all();
+}
+
+PreservedAnalyses DominatorTreeVerifierPass::run(Function &F,
+                                                 FunctionAnalysisManager &AM) {
+  AM.getResult<DominatorTreeAnalysis>(F).verifyDomTree();
+
+  return PreservedAnalyses::all();
+}
+
+//===----------------------------------------------------------------------===//
+//  DominatorTreeWrapperPass Implementation
+//===----------------------------------------------------------------------===//
+//
+// The implementation details of the wrapper pass that holds a DominatorTree
+// suitable for use with the legacy pass manager.
+//
+//===----------------------------------------------------------------------===//
+
+char DominatorTreeWrapperPass::ID = 0;
+INITIALIZE_PASS(DominatorTreeWrapperPass, "domtree",
+                "Dominator Tree Construction", true, true)
+
+bool DominatorTreeWrapperPass::runOnFunction(Function &F) {
+  DT.recalculate(F);
+  return false;
+}
+
+void DominatorTreeWrapperPass::verifyAnalysis() const {
+    if (VerifyDomInfo)
+      DT.verifyDomTree();
+}
+
+void DominatorTreeWrapperPass::print(raw_ostream &OS, const Module *) const {
+  DT.print(OS);
+}
+